In some catheterization techniques, it is desirable to use a series of catheters in order to complete effectively the procedure at hand. For example, in percutaneous transluminal coronary angioplasty procedures in which a balloon catheter is advanced into a stenosed region of the patient's coronary artery and is inflated within the stenosis to dilate the lumen of the artery, it is not uncommon for the physician to require the sequential use of several balloon dilatation catheters having balloons of progressively increasing size. Typically, such catheters are used in connection with a guidewire that extends through the catheter and serves as a guide over which the catheter may be advanced to the stenosis. When performing such a catheter exchange, it is important to do so without shifting and losing the position of the guidewire in the entry so that the guidewire may be used to guide the next catheter to the stenosis. In order to maintain guidewire position, conventional practice has been to use a relatively long exchange wire. The exchange wire, which typically is of the order of 300 cm long (as compared to a conventional guidewire length of the order of 175 cm) is first exchanged for the conventional guidewire by removing the conventional guidewire from the existing catheter and replacing it with the longer exchange wire. Then the existing catheter is withdrawn over the exchange wire, the exchange wire being sufficiently long so that it is never completely covered by the withdrawn catheter thereby enabling the exchange wire to be held in position by the physician or an assistant during the catheter withdrawal. After the initial catheter is removed, the succeeding catheter is advanced over the exchange wire which guides the second catheter to the stenosis. The exchange wire then may be removed and may be replaced with a conventional guidewire which, typically, will be more easily manipulated during the angioplasty procedure.
The foregoing procedures are time consuming and somewhat awkward. A significant advance in the technique for effecting catheter exchanges has been developed and has been in use which involves a system that enables exchange of catheters without using exchange wires. In brief, that system utilizes an extension wire that is attached to the proximal end of the guidewire already in place in the patient. That effectively extends the overall length of the guidewire to that needed for the catheter exchange. The system uses a connection in which the distal end of an extension wire is telescoped together with the proximal end of the guidewire and the junction then is crimped, thus, retaining the wires together by deforming them at their juncture. The crimp is intended to present low resistance to the catheter as it is passed over the connection. Some resistance, however, does result and it has not before been possible to completely eliminate the resistance presented by the crimp. Further inconvenience with the crimped system is that it requires the use of a separate crimping tool. When the guidewire and extension wire are detached, they cannot be reconnected or reused easily because of the deformation formed during their connection. Thus, some inconvenience is presented should it be desirable to make multiple catheter exchanges.
It is among the general objects of the invention to provide an improved connection system for a guidewire and an extension wire.